1. Field of the Invention
This invention relates to a weaving loom having an improved sley movement.
2. Description of the Prior Art
Weaving looms whose sley is driven by a knee mechanism are known. This knee mechanism is suitable for carrying out sley movement with double beat-up.
In Belgian Patent No. BE-895266 a weaving loom is disclosed in which the sley is provided with a pair of sley legs which are arranged in the form of a parallelogram support and the sley is further driven by such a knee mechanism which interacts with a cam. When the sley carries out such movement, the weaving reed maintains its vertical orientation during the oscillating beat-up movement, which takes place in the form of arcs on the sley legs with the parallelogram support. Using the knee mechanism, a large beat-up pressure force can be effected with a limited drive torque on the cam, as is well known in the field of mechanical presses.
However, a weaving loom of this kind has various disadvantages. In order to span a weaving width of large dimensions, this sley has to be designed such that it has great flexural stiffness, as only two drive points can be provided alongside the warp threads on both sides of the loom. Consequently, the sley has to be designed as a heavy girder supported by various parallelograms supporting legs which act as sley legs. Therefore, these sley legs do not contribute towards the flexural stiffness of the unit. In addition, the drive is only transmitted by two drive points which are located outside the fabric layer. This results in a considerable flexural strain on the sley. A sley construction of this kind is relatively heavy. This brings with it a high moment of inertia which has adverse effect on the weaving speeds and, in addition, also generates vibrations of the ground.
Document BE-900016 discloses a weaving loom which is provided with a sley having a parallelogram support and direct cam drive. With this weaving loom, effecting a double beat-up movement by means of the design of the cam profile is very difficult. The drive of the sley takes place over a large width by the twisting moment of one single reed rotary shaft. This reed rotary shaft thus has to be dimensioned to be large in order to be able to transmit the required twisting moment. Furthermore, the cam drives have to be fitted under the fabric layer in order to reduce the torsion arm. Fitting the drive groups under the fabric layer is relatively complicated and makes access for any repair work relatively difficult.